Ornamental plants such as begonias, geraniums, impatiens, poinsettias and the like comprise a large and profitable market in the United States. For example, sales of poinsettias, one of the best-selling flowering potted plants in the United States, exceeded $220 million dollars in 1998. Many ornamental plants such as poinsettias are vegetatively or clonally propagated (i.e., by cuttings from stock plants). Plants produced in this manner share the same genetic and phenotypic characteristics of the stock plant. Distributors, growers and buyers of ornamental plants are often concerned about the authenticity of the particular variety or cultivar of plant being grown or sold. Accordingly, a need exists for a method to reliably and accurately determine if a particular plant is the same cultivar as another cultivar, or if a particular plant is a member of a particular family or breeding program of plants. Additionally, a need exists for a method of accurately identifying particular cultivars by key characteristics, and then cataloging those characteristics such that plants produced in the future may be compared to the cataloged plants (i.e., in order to determine if a plant is a new cultivar or the same as one already known). Specifically, there is a need for a method that will significantly improve current visual techniques for cataloging that are both time-consuming for the practitioner and prone to producing ambiguous results.
One potential method of confirming the identity of a cultivar is to characterize key genetic traits or patterns of known cultivars, and then compare these traits or patterns with the genetic traits or patterns of the plant whose genetic identity is unknown. Genetic patterns of a particular plant may be obtained by producing a unique “fingerprint” of the genome of the plant, which fingerprint will identify that plant as being of a particular genotype or cultivar.
Over the past 10 years, genetic mapping technologies utilizing analyses of restriction fragment length polymorphisms (RFLP), random amplified polymorphic DNA (RAPD), simple sequence repeats (SSR) and amplified fragment length polymorphisms (AFLP) have been used for identifying genetic markers for desirable traits or phenotypes in plants. These techniques have also been useful adjuncts to genetic and breeding programs for genome mapping and marker-assisted selection, respectively. Using these technologies, attempts have been made to develop cultivar-specific fingerprints for identification.
Unfortunately, the RAPD and RFLP technologies used in previous attempts to fingerprint cultivars lacked the resolution to distinguish between genotypes. While AFLP and SSR techniques generally have sufficient resolution to distinguish between certain genotypes, these methods have heretofore been unable to overcome the problems posed by the inherent heterogeneity in regions of plant genomes that contain polymorphisms, but which are unrelated to the regions of the genomes that are related to cultivar identity. In particular, these technologies have been limited in their use for reliable cultivar identification of vegetatively propagated plants due to recognized and unrecognized regions of heterogeneity in these plant genomes.
Accordingly, the identification of a set of polymorphism-containing restriction fragments strictly associated with cultivar diversity in vegetatively propagated plants remains desirable. Once identified, such a set could be used, for example, to create reference databases containing fingerprints of particular cultivars. The ability to reliably compare fingerprints of individual plant genomes to polymorphic restriction fragments known to be related to cultivar identity would be of value to plant breeders, for example, in monitoring license agreements or authenticating plants that are patented. In plant breeding programs, these methods could be used for monitoring genetic drift and for trait or cultivar selection, while plant growers could use such methods to reliably confirm that they are receiving the cultivars they have purchased. Such methods have heretofore not been available.